California has the largest concentration of American Indians in the country. We propose to increase long-term smoking cessation among American Indians in the northern portion of the state through the application ofa provider-based intervention that can be reproduced throughout the nation. The research team assembled for this project draws from members of the Northern California Cancer Center consortium and is comprised of leaders of the American Indian community and researchers known for their work in smoking intervention. The target population for this project is comprised of approximately 75,000 American Indians in the NCCC service region in both urban and rural communities. Smoking cessation has been identified as the most needed area of cancer control intervention by the staff of the 17 clinics in the region, all of whom will participate in the proposed project. In the three-phased study design, a survey of 1500 clinic users will establish the prevalence of smoking and use of smokeless tobacco and identify correlates of tobacco use behavior. The physician-initiated "Quit for Life" smoking cessation intervention model will be modified for use among American Indians in their own clinics. A unique feature of the intervention will be follow-up home visits from Indian Community Health Representatives, already integral clinic team members. The second phase is a randomized clinical trial in which clinics will be randomly assigned to intervention or control groups. After training of physicians, dentists and clinic staff in the intervention clinics, 1400 patients will be consecu- tively recruited to participate in the trial, stratified by intervention status and urban/rural setting. Measurement of critical knowledge, attitudes and behaviors will be assessed at baseline, six months and 18 months. In the third phase, analyses will compare biochemically confirmed quit rates as well as motivation and attempts to quit, between intervention and control clinic participants. Quit rates among family members will also be evaluated as a measure of the diffusion of the intervention into the community. This project will thus produce reliable estimates of the prevalence of tobacco use in this population, a culturally appropriate, evaluated adaptation of an effective smoking cessation intervention, culturally specific health educational materials, and will provide the opportunity for American Indian investigators and health workers to develop experience and expertise in cancer control within their own communities.